The invention relates to an image transmission apparatus, and, more particularly, to an image transmission apparatus suitable for transmitting an image photographed by an electronic still camera or transmitting a static video image photographed by a video camera or an ITV camera.
As conventional ordinary image transmission apparatuses, transmission apparatuses 15a and 15b are known which are respectively connected to a transmission network 13b such as a public line, ISDN network, automobile telephone network, or the like, as shown in FIG. 2. The transmission apparatus 15a receives an image from a video floppy 1 or a video camera 3 and supplies data relating to the received image to the transmission network 13b through a transmission line 13a. The transmission apparatus 15b, on the other hand, receives the image data from the transmission network 13b and supplies an image relating to the received image data to a video printer 10 and a display 11 and also transmits the image to a data processing apparatus 16 through a transmission line 14a. The image processed by the data processing apparatus 16 is sent to a printer 17 and a display 18. As a structural arrangement of each of the transmission apparatuses 15a and 15b, a circuit construction such as shown in FIG. 1 is used.
That is, each of the transmission apparatuses 15a and 15b of a conventional ordinary image transmission apparatus are composed of: a reader 2; a color separating circuit 4; an A/D converting circuit 5; a sampling clock circuit 6; a frame memory 7; a display control circuit 8; a D/A converting circuit 9; a static image compressing/expanding circuit 12; a transmitting/receiving section 13; and a host interface circuit 14. The host interface circuit 14 is connected to the data processing apparatus 16 through the transmission line 14a. The transmitting/receiving section 13 is connected to the transmission network 13b through the transmission line 13a. When the reader 2 read image data stored in the video floppy 1, the read-out image data are supplied to the color separating circuit 4 as a video signal representing an image photographed by the electronic still camera. Further, a video signal representing an image photographed by the video camera 3 is also supplied to the color separating circuit 4. The color separating circuit 4 divides the video signal from the reader 2 or the video camera 3 into color signals of Y, U, and V or R, G, and B and a color burst signal. The color separating circuit 4 then supplies the color burst signal to the sampling clock circuit 6 and supplies the color signals to the A/D converting circuit 5. The A/D converting circuit 5 operates to quantize and sample the color signals in accordance with sampling clocks to thereby produce image data. The image data thus produced are stored in the frame memory 7. When the image data stored in the frame memory 7 is transmitted to an apparatus which is located at a distant place, the image data in the frame memory are supplied to and compressed by the static image compressing expanding circuit 12, and the image data, an amount of which has been reduced for data transmission, are transmitted from the transmitting/receiving section 13 to a public line, an ISDN network, an automobile telephone network, or the like through the transmission line 13a. Then, the image data are transmitted to the transmission apparatus 15b on the receiving side. The image data are received by the receiving side through the transmitting/receiving section 13 of the transmission apparatus 15b on the receiving side. The compressed and transmitted image data are expanded by the static image compressing/expanding circuit 12 and are stored in the frame memory 7. Thereafter, the image data are transferred to the video printer 10 and the display 11 through the display control circuit 8 and the D/A converting circuit 9. Thus, the received image data are printed by the video printer 10, and simultaneously an image thereof is displayed on a screen of the display 11.
On the other hand, the image data received by the host interface circuit 14 are transferred to the data processing apparatus 16 in FIG. 2 through the transmission line 14a to be stored in a data base so that a data base for the image data is provided. The image data are retrieved when required. The content of the image data is printed by the printer 17, or an image of the image data is displayed on a screen of the display 18.
In the above-described conventional transmission apparatuses, however, the number of pixels of an image is determined by a value which is a multiple of a clock frequency 3.48 MHz of a clock signal which is generated in the sampling clock circuit 6 by using a color burst signal. Therefore, in a number of transmission apparatuses, the number of horizontal.times.vertical pixels is chosen to be 768.times.480 pixels for a high definition type transmission apparatus, 384.times.240 pixels for a middle definition type transmission apparatus, and 192.times.120 pixels for a low definition type transmission apparatus. Therefore, in a printer 17 and a display 18 which are used in the data processing apparatus 16, etc., when a pixel number ratio between the horizontal pixels and the vertical pixels is chosen to be 1:1, there arises a problem that a reproduced image is deformed as compared with an original image.